Pressure pulse fracturing system

ABSTRACT

The present invention provides for an assembly for creating a pressure pulse in a liquid-filled cavity within a fracturable material such as a boulder wherein the primary energy storage element is disposed in a transducer at the boulder to improve the coupling of energy between the energy storage unit and the fluid in the boulder.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the filing of U.S. ProvisionalPatent Application Ser. No. 60/603,509, entitled “Electrocrushing FASTDrill and Technology, High Relative Permittivity Oil, High EfficiencyBoulder Breaker, New Electrocrushing Process, and Electrocrushing MiningMachine”, filed on Aug. 20, 2004, and the specification of thatapplication is incorporated herein by reference.

This application is also related to: U.S. utility application entitled“Pulsed Electric Rock Drilling Apparatus”, Ser. No. 11/208,671; U.S.utility application entitled “High Permittivity Fluid”, Ser. No.11/208,766; and U.S. utility application entitled “Virtual ElectrodeMineral Particle Disintegrator”, Ser. No. 11/208,950 all of which arebeing filed concurrently herewith, and the specification and claims ofthose applications are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention (Technical Field)

The present invention relates to pulse powered drilling apparatuses andmethods. The present invention also relates to insulating fluids of highrelative permittivity (dielectric constant).

2. Background Art

Processes using pulsed power technology are known in the art forbreaking mineral lumps. FIG. 1 shows a process by which a conductionpath or streamer is created inside rock to break it. An electricalpotential is impressed across the electrodes which contact the rock fromthe high voltage electrode 100 to the ground electrode 102. Atsufficiently high electric field, an arc 104 or plasma is formed insidethe rock 106 from the high voltage electrode to the low voltage orground electrode. The expansion of the hot gases created by the arcfractures the rock. When this streamer connects one electrode to thenext, the current flows through the conduction path, or arc, inside therock. The high temperature of the arc vaporizes the rock and any wateror other fluids that might be touching, or are near, the arc. Thisvaporization process creates high-pressure gas in the arc zone, whichexpands. This expansion pressure fails the rock in tension, thuscreating rock fragments.

The process of passing such a current through minerals is disclosed inU.S. Pat. No. 4,540,127 which describes a process for placing a lump ofore between electrodes to break it into monomineral grains. As noted inthe '127 patent, it is advantageous in such processes to use aninsulating liquid that has a high relative permittivity (dielectricconstant) to shift the electric fields away from the liquid and into therock in the region of the electrodes.

The '127 patent discusses using water as the fluid for the mineraldisintegration process. However, insulating drilling fluid must providehigh dielectric strength to provide high electric fields at theelectrodes, low conductivity to provide low leakage current during thedelay time from application of the voltage until the arc ignites in therock, and high relative permittivity to shift a higher proportion of theelectric field into the rock near the electrodes. Water provides highrelative permittivity, but has high conductivity, creating high electriccharge losses. Therefore, water has excellent energy storage properties,but requires extensive deionization to make it sufficiently resistive sothat it does not discharge the high voltage components by currentleakage through the liquid. In the deionized condition, water is verycorrosive and will dissolve many materials, including metals. As aresult, water must be continually conditioned to maintain the highresistivity required for high voltage applications. Even when deionized,water still has such sufficient conductivity that it is not suitable forlong-duration, pulsed power applications.

Petroleum oil, on the other hand, provides high dielectric strength andlow conductivity, but does not provide high relative permittivity.Neither water nor petroleum oil, therefore, provide all the featuresnecessary for effective drilling.

Propylene carbonate is another example of such insulating materials inthat it has a high dielectric constant and moderate dielectric strength,but also has high conductivity (about twice that of deionized water)making it unsuitable for pulsed power applications.

In addition to the high voltage, mineral breaking applications discussedabove, Insulating fluids are used for many electrical applications suchas, for example, to insulate electrical power transformers.

There is a need for an insulating fluid having a high dielectricconstant, low conductivity, high dielectric strength, and a long lifeunder industrial or military application environments.

Other techniques are known for fracturing rock. Systems known in the artas “boulder breakers” rely upon a capacitor bank connected by a cable toan electrode or transducer that is inserted into a rock hole. Suchsystems are described by Hamelin, M. and Kitzinger, F., Hard RockFragmentation with Pulsed Power, presented at the 1993 Pulsed PowerConference, and Res, J. and Chattapadhyay, A, “Disintegration of HardRocks by the Electrohydrodynamic Method” Mining Engineering, January1987. These systems are for fracturing boulders resulting from themining process or for construction without having to use explosives.Explosives create hazards for both equipment and personnel because offly rock and over pressure on the equipment, especially in undergroundmining. Because the energy storage in these systems are located remotelyfrom the boulder, efficiency is compromised. Therefore, there is a needfor improving efficiency in the boulder breaking and drilling processes.

Another technique for fracturing rock is the plasma-hydraulic (PH), orelectrohydraulic (EH) techniques using pulsed power technology to createunderwater plasma, which creates intense shock waves in water to crushrock and provide a drilling action. In practice, an electrical plasma iscreated in water by passing a pulse of electricity at high peak powerthrough the water. The rapidly expanding plasma in the water creates ashock wave sufficiently powerful to crush the rock. In such a process,rock is fractured by repetitive application of the shock wave.

BRIEF SUMMARY OF THE INVENTION

The present invention comprises a method and an assembly for creating apressure pulse in a liquid-filled cavity within a fracturable material.The preferred assembly comprises: a transducer; an energy storagecomponent disposed in the transducer; a cable connected to the storagecomponent for delivery of electric current; and a plurality ofelectrodes for converting the electrical current into a plasma pressuresource.

A switch is preferably disposed in the transducer to connect the energystorage component to the electrodes. A high voltage capacitor bankpreferably provides a high voltage pulse via the cable. The capacitorbank preferably includes, but is not limited to a spark gap, athyratron, a vacuum gap, a pseudo-spark switch, a mechanical switch,and/or a combination thereof.

The apparatus preferably further comprises an inductive storagecomponent to provide a high voltage pulse via the cable. The inventionfurther comprises a method and an assembly for creating pressure wavesin a liquid to fracture material. The assembly preferably comprises: atransducer; and one or more pairs of electrodes disposed on thetransducer, the electrodes defining a gap there between through which anelectrical current passes to create pressure through expansion of liquidas it undergoes a phase change to gas or plasma. Preferably, more thanone set of electrodes are arranged in parallel. Or, more than one set ofelectrodes is arranged a line or series of straight lines.Alternatively, more than one set of electrodes is arranged in ageometric configuration, including but not limited to a straight line, acurve, a circle, a spiral, and/or a combination thereof.

The electrode sets are preferably disposed in the transducer so that theelectrodes provide capacitance between each intermediate electrode andthe ground structure of the transducer. Capacitance is preferably formedvia a liquid disposed between the intermediate electrode and the groundstructure. The capacitance is preferably formed via a capacitor disposedbetween the intermediate electrode and the ground structure. Thecapacitor comprises a solid or liquid dielectric material. Preferably,there is a liquid or capacitor between the electrodes to form thecapacitance.

The assembly may further comprise an integral energy storage module tosupply electrical energy to a multi-gap transducer. The cable ispreferably connected to an energy storage device located away from thefracturable material.

The present invention provides for a more efficient delivery ofelectrical power to the mineral to be fractured.

The present invention also provides for a longer life for components.

Other objects, advantages and novel features, and further scope ofapplicability of the present invention will be set forth in part in thedetailed description to follow, taken in conjunction with theaccompanying drawings, and in part will become apparent to those skilledin the art upon examination of the following, or may be learned bypractice of the invention. The objects and advantages of the inventionmay be realized and attained by means of the instrumentalities andcombinations pointed out in the appended claims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The accompanying drawings, which are incorporated into and form a partof the specification, illustrate one or more embodiments of the presentinvention and, together with the description, serve to explain theprinciples of the invention. The drawings are only for the purpose ofillustrating one or more preferred embodiments of the invention and arenot to be construed as limiting the invention. In the drawings:

FIG. 1 shows an electrocrushing process of the prior art;

FIG. 2 shows an end view of a coaxial electrode set for a cylindricalbit of an embodiment of the present invention;

FIGS. 3A-C show alternate embodiments

FIG. 4 shows an alternate embodiment of a plurality of coaxial electrodesets;

FIG. 5 shows a conical bit of an embodiment of the present invention;

FIG. 6 is of a dual-electrode set bit of an embodiment of the presentinvention;

FIG. 7 is of a dual-electrode conical bit with two different cone anglesof an embodiment of the present invention;

FIGS. 8A and 8B show embodiments of a drill bit of the present inventionwherein one ground electrode is the tip of the bit and the other groundelectrode has the geometry of a great circle of the cone;

FIG. 9 shows the range of bit rotation azimuthal angle of an embodimentof the present invention;

FIG. 10 shows an embodiment of the drill bit of the present inventionhaving radiused electrodes;

FIG. 11 shows the complete drill assembly of an embodiment of thepresent invention;

FIG. 12 shows the reamer drag bit of an embodiment of the presentinvention;

FIG. 13 shows a solid-state switch or gas switch controlled high voltagepulse generating system that pulse charges the primary output capacitorof an embodiment of the present invention;

FIG. 14 shows an array of solid-state switch or gas switch controlledhigh voltage pulse generating circuits that are charged in parallel anddischarged in series to pulse-charge the output capacitor of anembodiment of the present invention;

FIG. 15 shows a voltage vector inversion circuit that produces a pulsethat is a multiple of the charge voltage of an embodiment of the presentinvention;

FIGS. 16A, 16B, and 16C show inductive store voltage gain systems toproduce the pulses needed for the FAST Drill of an embodiment of thepresent invention;

FIG. 17 shows a drill assembly powered by a fuel cell that is suppliedby fuel lines and exhaust line from the surface inside the continuousmetal mud pipe of an embodiment of the present invention;

FIG. 18 shows a roller-cone bit with an electrode set of an embodimentof the present invention;

FIG. 19 shows a small-diameter electrocrushing drill of an embodiment ofthe present invention;

FIG. 20 shows an electrocrushing vein miner of an embodiment of thepresent invention;

FIG. 21 shows a water treatment unit useable in the embodiments of thepresent invention;

FIG. 22 shows a high energy electrohydraulic boulder breaker system(HEEB) of an embodiment of the present invention;

FIG. 23 shows a transducer of the embodiment of FIG. 22;

FIG. 24 shows the details of the an energy storage module and transducerof the embodiment of FIG. 22;

FIG. 25 shows the details of an inductive storage embodiment of the highenergy electrohydraulic boulder breaker energy storage module andtransducer of an embodiment of the present invention;

FIG. 26 shows the embodiment of the high energy electrohydraulic boulderbreaker disposed on a tractor for use in a mining environment;

FIG. 27 shows a geometric arrangement of the embodiment of parallelelectrode gaps in a transducer in a spiral configuration.

FIG. 28 shows details of another embodiment of an electrohydraulicboulder breaker system;

FIG. 29 shows an embodiment of a virtual electrode electrocrushingprocess;

FIG. 30 shows an embodiment of the virtual electrode electrocrushingsystem comprising a vertical flowing fluid column;

FIG. 31 shows a pulsed power drilling apparatus manufactured and testedin accordance with an embodiment of the present invention; and

FIG. 32 is a graph showing dielectric strength versus delay to breakdownof the insulating formulation of the present invention, oil, and water.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides for pulsed power breaking and drillingapparatuses and methods. As used herein, “drilling” is defined asexcavating, boring into, making a hole in, or otherwise breaking anddriving through a substrate. As used herein, “bit” and “drill bit” aredefined as the working portion or end of a tool that performs a functionsuch as, but not limited to, a cutting, drilling, boring, fracturing, orbreaking action on a substrate (e.g., rock). As used herein, the term“pulsed power” is that which results when electrical energy is stored(e.g., in a capacitor or inductor) and then released into the load sothat a pulse of current at high peak power is produced.“Electrocrushing” (“EC”) is defined herein as the process of passing apulsed electrical current through a mineral substrate so that thesubstrate is “crushed” or “broken”.

Electrocrushing Bit

An embodiment of the present invention provides a drill bit on which isdisposed one or more sets of electrodes. In this embodiment, theelectrodes are disposed so that a gap is formed between them and aredisposed on the drill bit so that they are oriented along a face of thedrill bit. In other words, the electrodes between which an electricalcurrent passes through a mineral substrate (e.g., rock) are not onopposite sides of the rock. Also, in this embodiment, it is notnecessary that all electrodes touch the mineral substrate as the currentis being applied. In accordance with this embodiment, at least one ofthe electrodes extending from the bit toward the substrate to befractured and may be compressible (i.e., retractable) into the drill bitby any means known in the art such as, for example, via a spring-loadedmechanism.

Generally, but not necessarily, the electrodes are disposed on the bitsuch that at least one electrode contacts the mineral substrate to befractured and another electrode that usually touches the mineralsubstrate but otherwise may be close to, but not necessarily touching,the mineral substrate so long as it is in sufficient proximity forcurrent to pass through the mineral substrate. Typically, the electrodethat need not touch the substrate is the central, not the surrounding,electrode.

Therefore, the electrodes are disposed on a bit and arranged such thatelectrocrushing arcs are created in the rock. High voltage pulses areapplied repetitively to the bit to create repetitive electrocrushingexcavation events. Electrocrushing drilling can be accomplished, forexample, with a flat-end cylindrical bit with one or more electrodesets. These electrodes can be arranged in a coaxial configuration.

FIG. 2 shows an end view of such a coaxial electrode set configurationfor a cylindrical bit, showing high voltage or center electrode 108,ground or surrounding electrode 110, and gap 112 for creating the arc inthe rock. Variations on the coaxial configuration are shown in FIG. 3. Anon-coaxial configuration of electrode sets arranged in bit housing 114is shown in FIG. 4. FIGS. 3-4 show ground electrodes that are completedcircles. Other embodiments may comprise ground electrodes that arepartial circles, partial or compete ellipses, or partial or completeparabolas in geometric form.

For drilling larger holes, a conical bit is preferably utilized,especially if controlling the direction of the hole is important. Such abit may comprise one or more sets of electrodes for creating theelectrocrushing arcs and may comprise mechanical teeth to assist theelectrocrushing process. One embodiment of the conical electrocrushingbit has a single set of electrodes, preferably arranged coaxially on thebit, as shown in FIG. 5. In this embodiment, conical bit 118 comprises acenter electrode 108, the surrounding electrode 110, the bit case orhousing 114 and mechanical teeth 116 for drilling the rock. Either, orboth, electrodes may be compressible. The surrounding electrodepreferably has mechanical cutting teeth 109 incorporated into thesurface to smooth over the rough rock texture produced by theelectrocrushing process. In this embodiment, the inner portion of thehole is drilled by the electrocrushing portion (i.e., electrodes 108 and110) of the bit, and the outer portion of the hole is drilled bymechanical teeth 116. This results in high drilling rates, because themechanical teeth have good drilling efficiency at high velocity near theperimeter of the bit, but very low efficiency at low velocity near thecenter of the bit. The geometrical arrangement of the center electrodeto the ground ring electrode is conical with a range of cone angles from180 degrees (flat plane) to about 75 degrees (extended centerelectrode).

An alternate embodiment is to arrange a second electrode set on theconical portion of the bit. In such an embodiment, one set of theelectrocrushing electrodes operates on just one side of the bit cone inan asymmetrical configuration as exemplified in FIG. 6 which shows adual-electrode set conical bit, each set of electrodes comprising centerelectrode 108, surrounding electrode 110, bit case or housing 114,mechanical teeth 116, and drilling fluid passage 120.

The combination of the conical surface on the bit and the asymmetry ofthe electrode sets results in the ability of the dual-electrode bit toexcavate more rock on one side of the hole than the other and thus tochange direction. For drilling a straight hole, the repetition rate andpulse energy of the high voltage pulses to the electrode set on theconical surface side of the bit is maintained constant per degree ofrotation. However, when the drill is to turn in a particular direction,then for that sector of the circle toward which the drill is to turn,the pulse repetition rate (and/or pulse energy) per degree of rotationis increased over the repetition rate for the rest of the circle. Inthis fashion, more rock is removed by the conical surface electrode setin the turning direction and less rock is removed in the otherdirections (See FIG. 9, discussed in detail below). Because of theconical shape of the bit, the drill tends to turn into the section wheregreater amount of rock was removed and therefore control of thedirection of drilling is achieved.

In the embodiment shown in FIG. 6, most of the drilling is accomplishedby the electrocrushing (EC) electrodes, with the mechanical teethserving to smooth the variation in surface texture produced by the ECprocess. The mechanical teeth 116 also serve to cut the gauge of thehole, that is, the relatively precise, relatively smooth inside diameterof the hole. An alternate embodiment has the drill bit of FIG. 6 withoutmechanical teeth 116, all of the drilling being done by the electrodesets 108 and 110 with or without mechanical teeth 109 in the surroundingelectrode 110.

Alternative embodiments include variations on the configuration of theground ring geometry and center-to-ground ring geometry as for thesingle-electrode set bit. For example, FIG. 7 shows such an arrangementin the form of a dual-electrode conical bit comprising two differentcone angles with center electrodes 108, surrounding or ground electrodes110, and bit case or housing 114. In the embodiment shown, the groundelectrodes are tip electrode 111 and conical side ground electrodes 110which surround, or partially surround, high voltage electrodes 108 in anasymmetric configuration.

As shown in FIG. 7, the bit may comprise two or more separate coneangles to enhance the ability to control direction with the bit. Theelectrodes can be laid out symmetrically in a sector of the cone, asshown in FIG. 5 or in an asymmetric configuration of the electrodesutilizing ground electrode 111 as the center of the cone as shown inFIG. 7. Another configuration is shown in FIG. 8A in which groundelectrode 111 is at the tip of the bit and hot electrode 108 and otherground electrode 110 are aligned in great circles of the cone. FIG. 8Bshows an alternate embodiment wherein ground electrode 111 is the tip ofthe bit, other ground electrode 110 has the geometry of a great circleof the cone, and hot electrodes 108 are disposed there between. Also,any combination of these configurations may be utilized.

It should be understood that the use of a bit with an asymmetricelectrode configuration can comprise one or more electrode sets and neednot comprise mechanical teeth. It should also be understood thatdirectional drilling can be performed with one or more electrode sets.

The EC drilling process takes advantage of flaws and cracks in the rock.These are regions where it is easier for the electric fields tobreakdown the rock. The electrodes used in the bit of the presentinvention are usually large in area in order to intercept more flaws inthe rock and therefore improve the drilling rate, as shown in FIG. 5.This is an important feature of the invention because most electrodes inthe prior art are small to increase the local electric fieldenhancement.

FIG. 9 shows the range of bit rotation azimuthal angle 122 where therepetition rate or pulse energy is increased to increase excavation onthat side of the drill bit, compared to the rest of the bit rotationangle that has reduced pulse repetition rate or pulse energy 124. Thebit rotation is referenced to a particular direction relative to theformation 126, often magnetic north, to enable the correct drill holedirection change to be made. This reference is usually achieved byinstrumentation provided on the bit. When the pulsed power systemprovides a high voltage pulse to the electrodes on the side of the bit(See FIG. 6), an arc is struck between one hot electrode and one groundelectrode. This arc excavates a certain amount of rock out of the hole.By the time the next high voltage pulse arrives at the electrodes, thebit has rotated a certain amount, and a new arc is struck at a newlocation in the rock. If the repetition rate of the electrical pulses isconstant as a function of bit rotation azimuthal angle, the bit willdrill a straight hole. If the repetition rate of the electrical pulsesvaries as a function of bit rotation azimuthal angle, the bit will tendto drift in the direction of the side of the bit that has the higherrepetition rate. The direction of the drilling and the rate of deviationcan be controlled by controlling the difference in repetition rateinside the high repetition rate zone azimuthal angle, compared to therepetition rate outside the zone (See FIG. 9). Also, the azimuthal angleof the high repetition rate zone can be varied to control thedirectional drilling. A variation of the invention is to control theenergy per pulse as a function of azimuthal angle instead of, or inaddition to, controlling the repetition rate to achieve directionaldrilling.

Fast Drill System

Another embodiment of the present invention provides a drillingsystem/assembly utilizing the electrocrushing bits described herein andis designated herein as the FAST Drill system. A limitation in drillingrock with a drag bit is the low cutter velocity at the center of thedrill bit. This is where the velocity of the grinding teeth of the dragbit is the lowest and hence the mechanical drilling efficiency is thepoorest. Effective removal of rock in the center portion of the hole isthe limiting factor for the drilling rate of the drag bit. Thus, anembodiment of the FAST Drill system comprises a small electrocrushing(EC) bit (alternatively referred to herein as a FAST bit or FAST Drillbit) disposed at the center of a drag bit to drill the rock at thecenter of the hole. Thus, the EC bit removes the rock near the center ofthe hole and substantially increases the drilling rate. By increasingthe drilling rate, the net energy cost to drill a particular hole issubstantially reduced. This is best illustrated by the bit shown in FIG.5 (discussed above) comprising EC process electrodes 108 and 100 set atthe center of bit 114, surrounded by mechanical drag-bit teeth 116. Therock at the center of the bit is removed by the EC electrode set, andthe rock near the edge of the hole is removed by the mechanical teeth,where the tooth velocity is high and the mechanical efficiency is high.

As noted above, the function of the mechanical drill teeth on the bit isto smooth off the tops of the protrusions and recesses left by theelectrocrushing or plasma-hydraulic process. Because the electrocrushingprocess utilizes an arc through the rock to crush or fracture the rock,the surface of the rock is rough and uneven. The mechanical drill teethsmooth the surface of the rock, cutting off the tops of the protrusionsso that the next time the electrocrushing electrodes come around toremove more rock, they have a larger smoother rock surface to contactthe electrodes.

The EC bit preferably comprises passages for the drilling fluid to flushout the rock debris (i.e., cuttings) (See FIG. 6). The drilling fluidflows through passages inside the electrocrushing bit and then out]through passages 120 in the surface of the bit near the electrodes andnear the drilling teeth, and then flows up the side of the drill systemand the well to bring rock cuttings to the surface.

The EC bit may comprise an insulation section that insulates theelectrodes from the housing, the electrodes themselves, the housing, themechanical rock cutting teeth that help smooth the rock surface, and thehigh voltage connections that connect the high voltage power cable tothe bit electrodes.

FIG. 10 shows an embodiment of the Fast drill high voltage electrode 108and ground electrodes 110 that incorporate a radius 176 on theelectrode, with electrode radius 176 on the rock-facing side ofelectrodes 110. Radius 176 is an important feature of the presentinvention to allocate the electric field into the rock. The feature isnot obvious because electrodes from prior art were usually sharp toenhance the local electric field.

FIG. 11 shows an embodiment of the FAST Drill system comprising two ormore sectional components, including, but not limited to: (1) at leastone pulsed power FAST drill bit 114; (2) at least one pulsed powersupply 136; (3) at least one downhole generator 138; (4) at least oneoverdrive gear to rotate the downhole generator at high speed 140; (5)at least one downhole generator drive mud motor 144; (6) at least onedrill bit mud motor 146; (7) at least one rotating interface 142; (8) atleast one tubing or drill pipe for the drilling fluid 147; and (9) atleast one cable 148. Not all embodiments of the FAST Drill systemutilize all of these components. For example, one embodiment utilizescontinuous coiled tubing to provide drilling fluid to the drill bit,with a cable to bring electrical power from the surface to the pulsedpower system. That embodiment does not require a down-hole generator,overdrive gear, or generator drive mud motor, but does require adownhole mud motor to rotate the bit, since the tubing does not turn. Anelectrical rotating interface is required to transmit the electricalpower from the non-rotating cable to the rotating drill bit.

An embodiment utilizing a multi-section rigid drill pipe to rotate thebit and conduct drilling fluid to the bit requires a downhole generator,because a power cable cannot be used, but does not need a mud motor toturn the bit, since the pipe turns the bit. Such an embodiment does notneed a rotating interface because the system as a whole rotates at thesame rotation rate.

An embodiment utilizing a continuous coiled tubing to provide mud to thedrill bit, without a power cable, requires a down-hole generator,overdrive gear, and a generator drive mud motor, and also needs adownhole motor to rotate the bit because the tubing does not turn. Anelectrical rotating interface is needed to transmit the electricalcontrol and data signals from the non-rotating cable to the rotatingdrill bit.

An embodiment utilizing a continuous coiled tubing to provide drillingfluid to the drill bit, with a cable to bring high voltage electricalpulses from the surface to the bit, through the rotating interface,places the source of electrical power and the pulsed power system at thesurface. This embodiment does not need a down-hole generator, overdrivegear, or generator drive mud motor or downhole pulsed power systems, butdoes need a downhole motor to rotate the bit, since the tubing does notturn.

Still another embodiment utilizes continuous coiled tubing to providedrilling fluid to the drill bit, with a fuel cell to generate electricalpower located in the rotating section of the drill string. Power is fedacross the rotating interface to the pulsed power system, where the highvoltage pulses are created and fed to the FAST bit. Fuel for the fuelcell is fed down tubing inside the coiled tubing mud pipe.

An embodiment of the FAST Drill system comprises FAST bit 114, a dragbit reamer 150 (shown in FIG. 12), and a pulsed power system housing 136(FIG. 11).

FIG. 12 shows reamer drag bit 150 that enlarges the hole cut by theelectrocrushing FAST bit, drag bit teeth 152, and FAST bit attachmentsite 154. Reamer drag bit 150 is preferably disposed just above FAST bit114. This is a conical pipe section, studded with drill teeth, that isused to enlarge the hole drilled by the EC bit (typically, for example,approximately 7.5 inches in diameter) to the full diameter of the well(for example, to approximately 12.0 inches in diameter). The conicalshape of drag bit reamer 150 provides more cutting teeth for a givendiameter of hole, thus higher drilling rates. Disposed in the centerpart of the reamer section are several passages. There is a passage forthe power cable to go through to the FAST bit. The power cable comesfrom the pulsed power section located above and/or within the reamer andconnects to the FAST drill bit below the reamer. There are also passagesin the reamer that provide oil flow down to the FAST bit and passagesthat provide flushing fluid to the reamer teeth to help cut the rock andflush the cuttings from the reamer teeth.

Preferably, a pulse power system that powers the FAST bit is enclosed inthe housing of the reamer drag bit and the stem above the drag bit asshown in FIG. 11. This system takes the electrical power supplied to theFAST Drill for the electrocrushing FAST bit and transforms that powerinto repetitive high voltage pulses, usually over 100 kV. The repetitionrate of those pulses is controlled by the control system from thesurface or in the bit housing. The pulsed power system itself caninclude, but is not limited to:

(1) a solid state switch controlled or gas-switch controlled pulsegenerating system with a pulse transformer that pulse charges theprimary output capacitor (example shown in FIG. 13);

(2) an array of solid-state switch or gas-switch controlled circuitsthat are charged in parallel and in series pulse-charge the outputcapacitor (example shown in FIG. 14);

(3) a voltage vector inversion circuit that produces a pulse at abouttwice, or a multiple of, the charge voltage (example shown in FIG. 15);

(4) An inductive store system that stores current in an inductor, thenswitches it to the electrodes via an opening or transfer switch (exampleshown in FIG. 16); or

(5) any other pulse generation circuit that provides repetitive highvoltage, high current pulses to the FAST Drill bit.

FIG. 13 shows a solid-state switch or gas switch controlled high voltagepulse generating system that pulse charges the primary output capacitor164, showing generating means 156 to provide DC electrical power for thecircuit, intermediate capacitor electrical energy storage means 158,gas, solid-state, or vacuum switching means 160 to switch the storedelectrical energy into pulse transformer 162 voltage conversion meansthat charges output capacitive storage means 164 connecting to FAST bit114.

FIG. 14 shows an array of solid-state switch or gas switch 160controlled high voltage pulse generating circuits that are charged inparallel and discharged in series through pulse transformer 162 topulse-charge output capacitor 164.

FIG. 15 shows a voltage vector inversion circuit that produces a pulsethat is a multiple of the charge voltage. An alternate of the vectorinversion circuit that produces an output voltage of about twice theinput voltage is shown, showing solid-state switch or gas switchingmeans 160, vector inversion inductor 166, intermediate capacitorelectrical energy storage means 158 connecting to FAST bit 114.

FIG. 16 shows an inductive store voltage gain system to produce thepulses needed for the FAST Drill, showing the solid-state switch or gasswitching means 160, saturable pulse transformers 168, and intermediatecapacitor electrical energy storage means 158 connecting to the FAST bit114.

The pulsed power system is preferably located in the rotating bit, butmay be located in the stationary portion of the drill pipe or at thesurface.

Electrical power for the pulsed power system is either generated by agenerator at the surface, or drawn from the power grid at the surface,or generated down hole. Surface power is transmitted to the FAST drillbit pulsed power system either by cable inside the drill pipe orconduction wires in the drilling fluid pipe wall. In the preferredembodiment, the electrical power is generated at the surface, andtransmitted downhole over a cable 148 located inside the continuousdrill pipe 147 (shown in FIG. 11).

The cable is located in non-rotating flexible mud pipe (continuouscoiled tubing). Using a cable to transmit power to the bit from thesurface has advantages in that part of the power conditioning can beaccomplished at the surface, but has a disadvantage in the weight,length, and power loss of the long cable.

At the bottom end of the mud pipe is located the mud motor whichutilizes the flow of drilling fluid down the mud pipe to rotate the FASTDrill bit and reamer assembly. Above the pulsed power section, at theconnection between the mud pipe and the pulsed power housing, is therotating interface as shown in FIG. 11. The cable power is transmittedacross an electrical rotating interface at the point where the mud motorturns the drag bit. This is the point where relative rotation betweenthe mud pipe and the pulsed power housing is accommodated. The rotatingelectrical interface is used to transfer the electrical power from thecable or continuous tubing conduction wires to the pulsed power system.It also passes the drilling fluid from the non-rotating part to therotating part of the drill string to flush the cuttings from the ECelectrodes and the mechanical teeth. The pulsed power system is locatedinside the rigid drill pipe between the rotating interface and thereamer. High voltage pulses are transmitted inside the reamer to theFAST bit.

In the case of electrical power transmission through conduction wires inrigid rotating pipe, the rotating interface is not needed because thepulsed power system and the conduction wires are rotating at the samevelocity. If a downhole gearbox is used to provide a different rotationrate for the pulsed power/bit section from the pipe, then a rotatinginterface is needed to accommodate the electrical power transfer.

In another embodiment, power for the FAST Drill bit is provided by adownhole generator that is powered by a mud motor that is powered by theflow of the drilling fluid (mud) down the drilling fluid, rigid,multi-section, drilling pipe (FIG. 11). That mudflow can be converted torotational mechanical power by a mud motor, a mud turbine, or similarmechanical device for converting fluid flow to mechanical power. Bitrotation is accomplished by rotating the rigid drill pipe. With powergeneration via downhole generator, the output from the generator can beinside the rotating pulsed power housing so that no rotating electricalinterface is required (FIG. 11), and only a mechanical interface isneeded. The power comes from the generator to the pulsed power systemwhere it is conditioned to provide the high voltage pulses for operationof the FAST bit.

Alternatively, the downhole generator might be of the piezoelectric typethat provides electrical power from pulsation in the mud. Such fluidpulsation often results from the action of a mud motor turning the mainbit.

Another embodiment for power generation is to utilize a fuel cell in thenon-rotating section of the drill string. FIG. 17 shows an example of aFAST Drill system powered by fuel cell 170 that is supplied by fuellines and exhaust line 172 from the surface inside the continuous metalmud pipe 147. The power from fuel cell 170 is transmitted across therotating interface 142 to pulsed power system 136, and hence to FAST bit114. The fuel cell consumes fuel to produce electricity. Fuel lines areplaced inside the continuous coiled tubing, which provides drillingfluid to the drill bit, to provide fuel to the fuel cell, and to exhaustwaste gases. Power is fed across the rotating interface to the pulsedpower system, where the high voltage pulses are created and fed to theFAST bit.

As noted above, there are two primary means for transmitting drillingfluid (mud) from the surface to the bit: continuous flexible tubing orrigid multi-section drill pipe. The continuous flexible mud tubing isused to transmit mud from the surface to the rotation assembly wherepart of the mud stream is utilized to spin the assembly through a mudmotor, a mud turbine, or another rotation device. Part of the mudflow istransmitted to the FAST bits and reamer for flushing the cuttings up thehole. Continuous flexible mud tubing has the advantage that power andinstrumentation cables can be installed inside the tubing with themudflow. It is stationary and not used to transmit torque to therotating bit. Rigid multi-section drilling pipe comes in sections andcannot be used to house continuous power cable, but can transmit torqueto the bit assembly. With continuous flexible mud pipe, a mechanicaldevice such as, for example, a mud motor, or a mud turbine, is used toconvert the mud flow into mechanical rotation for turning the rotatingassembly. The mud turbine can utilize a gearbox to reduce therevolutions per minute. A downhole electric motor can alternatively beused for turning the rotating assembly. The purpose of the rotatingpower source is primarily to provide torque to turn the teeth on thereamer and the FAST bit for drilling. It also rotates the FAST bit toprovide the directional control in the cutting of a hole. Anotherembodiment is to utilize continuous mud tubing with downhole electricpower generation.

In one embodiment, two mud motors or mud turbines are used: one torotate the bits, and one to generate electrical power.

Another embodiment of the rigid multi-section mud pipe is the use ofdata transmitting wires buried in the pipe such as, for example, theIntelipipe manufactured by Grant Prideco. This is a composite pipe thatuses magnetic induction to transmit data across the pipe joints, whiletransmitting it along wires buried in the shank of the pipe sections.Utilizing this pipe provides for data transmission between the bit andthe control system on the surface, but still requires the use ofdownhole power generation.

Another embodiment of the FAST Drill is shown in FIG. 18 wherein rotaryor roller-cone bit 174 is utilized, instead of a drag bit, to enlargethe hole drilled by the FAST bit. Roller-cone bit 174 compriseselectrodes 108 and 110 disposed in or near the center portion of rollercone bit 174 to excavate that portion of the rock where the efficiencyof the roller bit is the least.

Another embodiment of the rotating interface is to use a rotatingmagnetic interface to transfer electrical power and data across therotating interface, instead of a slip ring rotating interface.

In another embodiment, the mud returning from the well loaded withcuttings flows to a settling pond, at the surface, where the rockfragments settle out. The mud then cleaned and reinjected into the FASTDrill mud pipe.

Electrocrushing Vein Miner

Another embodiment of the present invention provides a small-diameter,electrocrushing drill (designated herein as “SED”) that is related tothe hand-held electrohydraulic drill disclosed in U.S. Pat. No.5,896,938 (to a primary inventor herein), incorporated herein byreference. However, the SED is distinguishable in that the electrodes inthe SED are spaced in such a way, and the rate of rise of the electricfield is such, that the rock breaks down before the water breaks down.When the drill is near rock, the electric fields break down the rock andcurrent passes through the rock, thus fracturing the rock into smallpieces. The electrocrushing rock fragmentation occurs as a result oftensile failure caused by the electrical current passing through therock, as opposed to compressive failure caused by the electrohydraulic(EH) shock or pressure wave on the rock disclosed in U.S. Pat. No.5,896,938, although the SED, too, can be connected via a cable from abox as described in the '938 patent so that it can be portable. FIG. 19shows a SED drill bit comprising case 206, internal insulator 208, andcenter electrode 210 which is preferably movable (e.g., spring-loaded)to maintain contact with the rock while drilling. Although case 206 andinternal insulator 208 are shown as providing an enclosure for centerelectrode 210, other components capable of providing an enclosure may beutilized to house electrode 210 or any other electrode incorporated inthe SED drill bit. Preferably, case 206 of the SED is the groundelectrode, although a separate ground electrode may be provided. Also,it should be understood that more than one set of electrodes may beutilized in the SED bit. A pulsed power generator as described in otherembodiments herein is linked to said drill bit for delivering highvoltage pulses to the electrode. In an embodiment of the SED, cable 207(which may be flexible) is provided to link a generator to theelectrode(s). A passage, for example cable 207, is preferably used todeliver water down the SED drill.

This SED embodiment is advantageous for drilling in non-porous rock.Also, this embodiment benefits from the use concurrent use of the highpermittivity liquid discussed herein.

Another embodiment of the present invention is to assemble severalindividual SED drill heads or electrode sets together into an array orgroup of drills, without the individual drill housings, to provide thecapability to mine large areas of rock. In such an embodiment, a vein ofore can be mined, leaving most of the waste rock behind. FIG. 20 showssuch an embodiment of a mineral vein mining machine herein designatedElectrocrushing Vein Miner (EVM) 212 comprising a plurality of SEDdrills 214, SED case 206, SED insulator 208, and SED center electrode210. This assembly can then be steered as it moves through the rock byvarying the repetition rate of the high voltage pulses differentiallyamong the drill heads. For example, if the repetition rate for the toprow of drill heads is twice as high but contains the same energy perpulse as the repetition rate for the lower two rows of drill heads, thepath of the mining machine will curve in the direction of the upper rowof drill heads, because the rate of rock excavation will be higher onthat side. Thus, by varying the repetition rate and/or pulse energy ofthe drill heads, the EVM can be steered dynamically as it is excavatinga vein of ore. This provides a very useful tool for efficiently miningjust the ore from a vein that has substantial deviation in direction.

In another embodiment, a combination of electrocrushing andelectrohydraulic (EH) drill bit heads enhances the functionality of theEVM by enabling the EVM to take advantage of ore structures that arelayered. Where the machine is mining parallel to the layers, as is thecase in mining most veins of ore, the shock waves from the EH drill bitheads tend to separate the layers, thus synergistically coupling to theexcavation created by the EC electrodes. In addition, combiningelectrocrushing drill heads with plasma-hydraulic drill heads combinesthe compressive rock fracturing capability of the plasma-hydraulic drillheads with the tensile rock failure of the EC drill heads to moreefficiently excavate rock.

With the EVM mining machine, ore can be mined directly and immediatelytransported to a mill by water transport, already crushed, so the energycost of primary crushing and the capital cost of the primary crushers issaved. This method has a great advantage over conventional mechanicalmethods in that it combines several steps in ore processing, and itgreatly reduces the amount of waste rock that must be processed. Thismethod of this embodiment can also be used for tunneling.

The high voltage pulses can be generated in the housing of the EVM,transmitted to the EVM via cables, or both generated elsewhere andtransmitted to the housing for further conditioning. The electricalpower generation can be at the EVM via fuel cell or generator, ortransmitted to the EVM via power cable. Typically, water or mining fluidflows through the structure of the EVM to flush out rock cuttings.

If a few, preferably just three, of the EC or PH drill heads shown inFIG. 20 are placed in a housing, the assembly can be used to drillholes, with directional control by varying the relative repetition rateof the pulses driving the drill heads. The drill will tend to drift inthe direction of the drill head with the highest pulse repletion rate,highest pulse energy, or highest average power. This electrocrushing (orEH) drill can create very straight holes over a long distance forimproving the efficiency of blasting in underground mining, or it can beused to place explosive charges in areas not accessible in a straightline.

Insulating Drilling Fluid

An embodiment of the present invention also comprises insulatingdrilling fluids that may be utilized in the drilling methods describedherein. For example, for the electrocrushing process to be effective inrock fracturing or crushing, it is preferable that the dielectricconstant of the insulating fluid be greater than the dielectric constantof the rock and that the fluid have low conductivity such as, forexample, a conductivity of less than approximately 10⁻⁶ mho/cm and adielectric constant of at least approximately 6.

Therefore, one embodiment of the present invention provides for aninsulating fluid or material formulation of high permittivity, ordielectric constant, and high dielectric strength with low conductivity.The insulating formulation comprises two or more materials such that onematerial provides a high dielectric strength and another provides a highdielectric constant. The overall dielectric constant of the insulatingformulation is a function of the ratio of the concentrations of the atleast two materials. The insulating formulation is particularlyapplicable for use in pulsed power applications.

Thus, this embodiment of the present invention provides for anelectrical insulating formulation that comprises a mixture of two ormore different materials. In one embodiment, the formulation comprises amixture of two carbon-based materials. The first material preferablycomprises a dielectric constant of greater than approximately 2.6, andthe second material preferably comprises a dielectric constant greaterthan approximately 10.0. The materials are at least partly miscible withone another, and the formulation preferably has low electricalconductivity. The term “low conductivity” or “low electricalconductivity”, as used throughout the specification and claims means aconductivity less than that of tap water, preferably lower thanapproximately 10⁻⁵ mho/cm, more preferably lower than 10⁻⁶ mho/cm.Preferably, the materials are substantially non-aqueous. The materialsin the insulating formulation are preferably non-hazardous to theenvironment, preferably non-toxic, and preferably biodegradable. Theformulation exhibits a low conductivity.

In one embodiment, the first material preferably comprises one or morenatural or synthetic oils. Preferably, the first material comprisescastor oil, but may comprise or include other oils such as, for example,jojoba oil or mineral oil.

Castor oil (glyceryl triricinoleate), a triglyceride of fatty acids, isobtained from the seed of the castor plant. It is nontoxic andbiodegradable. A transformer grade castor oil (from CasChem, Inc.) has adielectric constant (i.e., relative permittivity) of approximately 4.45at a temperature of approximately 22° C. (100 Hz).

The second material comprises a solvent, preferably one or morecarbonates, and more preferably one or more alkylene carbonates such as,but not limited to, ethylene carbonate, propylene carbonate, or butylenecarbonate. The alkylene carbonates can be manufactured, for example,from the reaction of ethylene oxide, propylene oxide, or butylene oxideor similar oxides with carbon dioxide.

Other oils, such as vegetable oil, or other additives can be added tothe formulation to modify the properties of the formulation. Solidadditives can be added to enhance the dielectric or fluid properties ofthe formulation.

The concentration of the first material in the insulating formulationranges from between approximately 1.0 and 99.0 percent by volume,preferably from between approximately 40.0 and 95.0 percent by volume,more preferably still from between approximately 65.0 and 90.0 percentby volume, and most preferably from between approximately 75.0 and 85.0percent by volume.

The concentration of the second material in the insulating formulationranges from between approximately 1.0 and 99.0 percent by volume,preferably from between approximately 5.0 and 60.0 percent by volume,more preferably still from between approximately 10.0 and 35.0 percentby volume, and most preferably from between approximately 15.0 and 25.0percent by volume.

Thus, the resulting formulation comprises a dielectric constant that isa function of the ratio of the concentrations of the constituentmaterials. The preferred mixture for the formulation of the presentinvention is a combination of butylene carbonate and a high permittivitycastor oil wherein butylene carbonate is present in a concentration ofapproximately 20% by volume. This combination provides a high relativepermittivity of approximately 15 while maintaining good insulationcharacteristics. In this ratio, separation of the constituent materialsis minimized. At a ratio of below 32%, the castor oil and butylenecarbonate mix very well and remain mixed at room temperature. At abutylene carbonate concentration of above 32%, the fluids separate ifundisturbed for approximately 10 hours or more at room temperature. Aproperty of the present invention is its ability to absorb water withoutapparent effect on the dielectric performance of the insulatingformulation.

An embodiment of the present invention comprising butylene carbonate incastor oil comprises a dielectric strength of at least approximately 300kV/cm (1 μsec), a dielectric constant of approximately at least 6, aconductivity of less than approximately 10⁻⁵ mho/cm, and a waterabsorption of up to 2,000 ppm with no apparent negative effect caused bysuch absorption. More preferably, the conductivity is less thanapproximately 10⁻⁶ mho/cm.

The formulation of the present invention is applicable to a number ofpulsed power machine technologies. For example, the formulation isuseable as an insulating and drilling fluid for drilling holes in rockor other hard materials or for crushing such materials as provided forherein. The use of the formulation enables the management of theelectric fields for electrocrushing rock. Thus, the present inventionalso comprises a method of disposing the insulating formulation about adrilling environment to provide electrical insulation during drilling.

Other formulations may be utilized to perform the drilling operationsdescribed herein. For example, in another embodiment, crude oil with thecorrect high relative permittivity derived as a product stream from anoil refinery may be utilized. A component of vacuum gas crude oil hashigh molecular weight polar compounds with O and N functionality.Developments in chromatography allow such oils to be fractionated bypolarity. These are usually cracked to produce straight hydrocarbons,but they may be extracted from the refinery stream to provide highpermittivity oil for drilling fluid.

Another embodiment comprises using specially treated waters. Such watersinclude, for example, the Energy Systems Plus (ESP) technology ofComplete Water Systems which is used for treating water to grow crops.In accordance with this embodiment, FIG. 21 shows water or a water-basedmixture 128 entering a water treatment unit 130 that treats the water tosignificantly reduce the conductivity of the water. The treated water132 then is used as the drilling fluid by the FAST Drill system 134. TheESP process treats water to reduce the conductivity of the water toreduce the leakage current, while retaining the high permittivity of thewater.

High Efficiency Electrohydraulic Boulder Breaker

Another embodiment of the present invention provides a high efficiencyelectrohydraulic boulder breaker (designated herein as “HEEB”) forbreaking up medium to large boulders into small pieces. This embodimentprevents the hazard of fly rock and damage to surrounding equipment. TheHEEB is related to the High Efficiency Electrohydraulic Pressure WaveProjector disclosed in U.S. Pat. No. 6,215,734 (to the principalinventor herein), incorporated herein by reference.

FIG. 22 shows the HEEB system disposed on truck 181, comprisingtransducer 178, power cable 180, and fluid 182 disposed in a hole.Transducer 178 breaks the boulder and cable 180 (which may be of anydesired length such as, for example, 6-15 m long) connects transducer178 to electric pulse generator 183 in truck 181. An embodiment of theinvention comprises first drilling a hole into a boulder utilizing aconventional drill, filling the hole is filled with water or aspecialized insulating fluid, and inserting HEEB transducer 178 into thehole in the boulder. FIG. 23 shows HEEB transducer 178 disposed inboulder 186 for breaking the boulder, cable 180, and energy storagemodule 184.

Main capacitor bank 183 (shown in FIG. 22) is first charged by generator179 (shown in FIG. 22) disposed on truck 181. Upon command, controlsystem 192 (shown in FIG. 22 and disposed, for example, in a truck) isclosed connecting capacitor bank 183 to cable 180. The electrical pulsetravels down cable 180 to energy storage module 184 where itpulse-charges capacitor set 158 (example shown in FIG. 24), or otherenergy storage devices (example shown in FIG. 25).

FIG. 24 shows the details of the HEEB energy storage module 184 andtransducer 178, showing capacitors 158 in module 184, and floatingelectrodes 188 in transducer 178.

FIG. 25 shows the details of the inductive storage embodiment of HEEBenergy storage module 184 and transducer 178, showing inductive storageinductors 190 in module 184, and showing the transducer embodiment ofparallel electrode gaps 188 in transducer 178. The transducer embodimentof parallel electrode gaps (FIG. 25) and series electrode gaps (FIG. 24)can reach be used alternatively with either the capacitive energy store158 of FIG. 24 or the inductive energy store 190 of FIG. 25.

These capacitors/devices are connected to the probe of the transducerassembly where the electrodes that create the pressure wave are located.The capacitors increase in voltage from the charge coming through thecable from the main capacitor bank until they reach the breakdownvoltage of the electrodes inside the transducer assembly. When the fluidgap at the tip of the transducer assembly breaks down (acting like aswitch), current then flows from the energy storage capacitors orinductive devices through the gap. Because the energy storage capacitorsare located very close to the transducer tip, there is very littleinductance in the circuit and the peak current through the transducersis very high. This high peak current results in a high energy transferefficiency from the energy storage module capacitors to the plasma inthe fluid. The plasma then expands, creating a pressure wave in thefluid, which fractures the boulder.

The HEEB system may be transported and used in various environmentsincluding, but not limited to, being mounted on a truck as shown in FIG.22 for transport to various locations, used for either underground oraboveground mining applications as shown in FIG. 26, or used inconstruction applications. FIG. 26 shows an embodiment of the HEEBsystem placed on a tractor for use in a mining environment and showingtransducer 178, power cable 180, and control panel 192.

Therefore, the HEEB does not rely on transmitting the boulder-breakingcurrent over a cable to connect the remote (e.g., truck mounted)capacitor bank to an electrode or transducer located in the rock hole.Rather, the HEEB puts the high current energy storage directly at theboulder. Energy storage elements, such as capacitors, are built into thetransducer assembly. Therefore, this embodiment of the present inventionincreases the peak current through the transducer and thus improves theefficiency of converting electrical energy to pressure energy forbreaking the boulder. This embodiment of the present invention alsosignificantly reduces the amount of current that has to be conductedthrough the cable thus reducing losses, increasing energy transferefficiency, and increasing cable life.

An embodiment of the present invention improves the efficiency ofcoupling the electrical energy to the plasma into the water and hence tothe rock by using a multi-gap design. A problem with the multi-gap waterspark gaps has been getting all the gaps to ignite because thecumulative breakdown voltage of the gaps is much higher than thebreakdown voltage of a single gap. However, if capacitance is placedfrom the intermediate gaps to ground (FIG. 24), each gap ignites at avoltage similar to the ignition voltage of a single gap. Thus, a largenumber of gaps can be ignited at a voltage of approximately a factor of2 greater than the breakdown voltage for a single gap. This improves thecoupling efficiency between the pulsed power module and the energydeposited in the fluid by the transducer. Holes in the transducer caseare provided to let the pressure from the multiple gaps out into thehole and into the rock to break the rock (FIG. 24).

In another embodiment, the multi-gap transducer design can be used witha conventional pulsed power system, where the capacitor bank is placedat some distance from the material to be fractured, a cable is run tothe transducer, and the transducer is placed in the hole in the boulder.Used with the HEEB, it provides the advantage of the much higher peakcurrent for a given stored energy.

Thus, an embodiment of the present invention provides a transducerassembly for creating a pressure pulse in water or some other liquid ina cavity inside a boulder or some other fracturable material, saidtransducer assembly incorporating energy storage means located directlyin the transducer assembly in close proximity to the boulder or otherfracturable material. The transducer assembly incorporates a connectionto a cable for providing charging means for the energy storage elementsinside the transducer assembly. The transducer assembly includes anelectrode means for converting the electrical current into a plasmapressure source for fracturing the boulder or other fracturablematerial.

Preferably, the transducer assembly has a switch located inside thetransducer assembly for purposes of connecting the energy storage moduleto said electrodes. Preferably, in the transducer assembly, the cable isused to pulse charge the capacitors in the transducer energy storagemodule. The cable is connected to a high voltage capacitor bank orinductive storage means to provide the high voltage pulse.

In another embodiment, the cable is used to slowly charge the capacitorsin the transducer energy storage module. The cable is connected to ahigh voltage electric power source.

Preferably, the switch located at the primary capacitor bank is a sparkgap, thyratron, vacuum gap, pseudo-spark switch, mechanical switch, orsome other means of connecting a high voltage or high current source tothe cable leading to the transducer assembly.

In another embodiment, the transducer electrical energy storage utilizesinductive storage elements.

Another embodiment of the present invention provides a transducerassembly for the purpose of creating pressure waves from the passage ofelectrical current through a liquid placed between one or more pairs ofelectrodes, each gap comprising two or more electrodes between whichcurrent passes. The current creates a phase change in the liquid, thuscreating pressure in the liquid from the change of volume due to thephase change. The phase change includes a change from liquid to gas,from gas to plasma, or from liquid to plasma.

Preferably, in the transducer, more than one set of electrodes isarranged in series such that the electrical current flowing through oneset of electrodes also flows through the second set of electrodes, andso on. Thus, a multiplicity of electrode sets can be powered by the sameelectrical power circuit.

In another embodiment, in the transducer, more than one set ofelectrodes is arranged in parallel such that the electrical current isdivided as it flows through each set of electrodes (FIG. 25). Thus, amultiplicity of electrode sets can be powered by the same electricalpower circuit.

Preferably, a plurality of electrode sets is arrayed in a line or in aseries of straight lines.

In another embodiment, the plurality of electrode sets is alternativelyarrayed to form a geometric figure other than a straight line,including, but not limited to, a curve, a circle (FIG. 25), or a spiral.FIG. 27 shows a geometric arrangement of the embodiment comprisingparallel electrode gaps 188 in the transducer 178, in a spiralconfiguration.

Preferably, the electrode sets in the transducer assembly areconstructed in such a way as to provide capacitance between eachintermediate electrode and the ground structure of the transducer (FIG.24).

In another embodiment, in the plurality of electrode sets, thecapacitance of the intermediate electrodes to ground is formed by thepresence of a liquid between the intermediate electrode and the groundstructure.

In another embodiment, in the plurality of electrode sets, thecapacitance is formed by the installation of a specific capacitorbetween each intermediate electrode and the ground structure (FIG. 24).The capacitor can use solid or liquid dielectric material.

In another embodiment, in the plurality of electrode sets, capacitanceis provided between the electrode sets from electrode to electrode. Thecapacitance can be provided either by the presence of the fracturingliquid between the electrodes or by the installation of a specificcapacitor from an intermediate electrode between electrodes as shown inFIG. 28. FIG. 28 shows the details of the HEEB transducer 178 installedin hole 194 in boulder 186 for breaking the boulder. Shown are cable180, the floating electrodes 188 in the transducer and liquid betweenthe electrodes 196 that provides capacitive coupling electrode toelectrode. Openings 198 in the transducer which allow the pressure waveto expand into the rock hole are also shown.

Preferably in the multi-electrode transducer, the electrical energy issupplied to the multi-gap transducer from an integral energy storagemodule.

Preferably in the multi-electrode transducer, the energy is supplied tothe transducer assembly via a cable connected to an energy storagedevice located away from the boulder or other fracturable material.

Virtual Electrode Electro-Crushing Process

Another embodiment of the present invention comprises a method forcrushing rock by passing current through the rock using electrodes thatdo not touch the rock. In this method, the rock particles are suspendedin a flowing or stagnant water column, or other liquid of relativepermittivity greater than the permittivity of the rock being fractured.Water is preferred for transporting the rock particles because thedielectric constant of water is approximately 80 compared to thedielectric constant of rock which is approximately 3.5 to 12.

In the preferred embodiment, the water column moves the rock particlespast a set of electrodes as an electrical pulse is provided to theelectrodes. As the electric field rises on the electrodes, thedifference in dielectric constant between the water and the rockparticle causes the electric fields to be concentrated in the rock,forming a virtual electrode with the rock. This is illustrated in FIG.29 showing rock particle 200 between high voltage electrodes 202 andground electrode 203 in liquid 204 whose dielectric constant issignificantly higher than that of rock particle 200.

The difference in dielectric constant concentrated the electric fieldsin the rock particle. These high electric fields cause the rock to breakdown and current to flow from the electrode, through the water, throughthe rock particles, through the conducting water, and back to theopposite electrode. In this manner, many small particles of rock can bedisintegrated by the virtual electrode electrocrushing method withoutany of them physically contacting both electrodes. The method is alsosuitable for large particles of rock.

Thus, it is not required that the rocks be in contact with the physicalelectrodes and so the rocks need not be sized to match the electrodespacing in order for the process to function. With the virtual electrodeelectrocrushing method, it is not necessary for the rocks to actuallytouch the electrode, because in this method, the electric fields areconcentrated in the rock by the high dielectric constant (relativepermittivity) of the water or fluid. The electrical pulse must be tunedto the electrical characteristics of the column structure and liquid inorder to provide a sufficient rate of rise of voltage to achieve theallocation of electric field into the rock with sufficient stress tofracture the rock.

Another embodiment of the present invention, illustrated in FIG. 30,comprises a reverse-flow electro-crusher wherein electrodes 202 send anelectrocrushing current to mineral (e.g., rock) particles 200 andwherein water or fluid 204 flows vertically upward at a rate such thatparticles 200 of the size desired for the final product are sweptupward, and whereas particles that are oversized sink downward.

As these oversized particles sink past the electrodes, a high voltagepulse is applied to the electrodes to fracture the particles, reducingthem in size until they become small enough to become entrained by thewater or fluid flow. This method provides a means of transporting theparticles past the electrodes for crushing and at the same timedifferentiating the particle size.

The reverse-flow crusher also provides for separating ash from coal inthat it provides for the ash to sink to the bottom and out of the flow,while the flow provides transport of the fine coal particles out of thecrusher to be processed for fuel.

INDUSTRIAL APPLICABILITY

The invention is further illustrated by the following non-limitingexample(s).

EXAMPLE 1

An apparatus utilizing FAST Drill technology in accordance with thepresent invention was constructed and tested. FIG. 31 shows FAST Drillbit 114, the drill stem 216, the hydraulic motor 218 used to turn drillstem 216 to provide power to mechanical teeth disposed on drill bit 114,slip ring assembly 220 used to transmit the high voltage pulses to theFAST bit 114 via a power cable inside drill stem 216, and tank 222 usedto contain the rocks being drilled. A pulsed power system, contained ina tank (not shown), generated the high voltage pulses that were fed intothe slip ring assembly. Tests were performed by conducting 150 kV pulsesthrough drill stem 216 to the FAST Bit 114, and a pulsed power systemwas used for generating the 150 kV pulses. A drilling fluid circulationsystem was incorporated to flush out the cuttings. The drill bit shownin FIG. 5 was used to drill a 7 inch diameter hole approximately 12inches deep in rock located in a rock tank. A fluid circulation systemflushed the rock cuttings out of the hole, cleaned the cuttings out ofthe fluid, and circulated the fluid through the system.

EXAMPLE II

A high permittivity fluid comprising a mixture of castor oil andapproximately 20% by volume butylene carbonate was made and tested inaccordance with the present invention as follows.

1. Dielectric Strength Measurements

Because this insulating formulation of the present invention is intendedfor high voltage applications, the properties of the formulation weremeasured in a high voltage environment. The dielectric strengthmeasurements were made with a high voltage Marx bank pulse generator, upto 130 kV. The rise time of the Marx bank was less than 100 nsec. Thebreakdown measurements were conducted with 1-inch balls immersed in theinsulating formulation at spacings ranging from 0.06 to 0.5 cm to enableeasy calculation of the breakdown fields. The delay from the initiationof the pulse to breakdown was measured. FIG. 32 shows the electric fieldat breakdown plotted as a function of the delay time in microseconds.Also included are data from the Charlie Martin models for transformeroil breakdown and for deionized water breakdown (Martin, T. H., A. H.Guenther, M Kristiansen “J. C. Martin on Pulsed Power” Lernum Press,(1996)).

The breakdown strength of the formulation is substantially higher thantransformer oil at times greater than 10 μsec. No special effort wasexpended to condition the formulation. It contained dust, dissolvedwater and other contaminants, whereas the Martin model is for very wellconditioned transformer oil or water.

2. Dielectric Constant Measurements.

The dielectric constant was measured with a ringing waveform at 20 kV.The ringing high voltage circuit was assembled with 8-inch diametercontoured plates immersed in the insulating formulation at 0.5-inchspacing. The effective area of the plates, including fringing fieldeffects, was calibrated with a fluid whose dielectric constant was known(i.e., transformer oil). An aluminum block was placed between the platesto short out the plates so that the inductance of the circuit could bemeasured with a known circuit capacitance. Then, the plates wereimmersed in the insulating formulation, and the plate capacitance wasevaluated from the ringing frequency, properly accounting for theeffects of the primary circuit capacitor. The dielectric constant wasevaluated from that capacitance, utilizing the calibrated effective areaof the plate. These tests indicated a dielectric constant ofapproximately 15.

3. Conductivity Measurements.

To measure the conductivity, the same 8-inch diameter plates used in thedielectric constant measurement were utilized to measure the leakagecurrent. The plates were separated by 2-inch spacing and immersed in theinsulating formulation. High voltage pulses, ranging from 70-150 kV wereapplied to the plates, and the leakage current flow between the plateswas measured. The long duration current, rather than the initialcurrent, was the value of interest, in order to avoid displacementcurrent effects. The conductivity obtained was approximately 1micromho/cm [1×10⁻⁶ (ohm-cm)^(−1].)

4. Water Absorption.

The insulating formulation has been tested with water content up to 2000ppm without any apparent effect on the dielectric strength or dielectricconstant. The water content was measured by Karl Fisher titration.

5. Energy Storage Comparison.

The energy storage density of the insulating formulation of the presentinvention was shown to be substantially higher than that of transformeroil, but less than that of deionized water. Table 1 shows the energystorage comparison of the insulating formulation, a transformer oil, andwater in the 1 μsec and 10 μsec breakdown time scales. The energydensity (in joules/cm³) was calculated from the dielectric constant(∈,∈₀) and the breakdown electric field (E_(bd)˜kV/cm). The energystorage density of the insulating formulation is approximatelyone-fourth that of water at 10 microseconds. The insulating formulationdid not require continuous conditioning, as did a water dielectricsystem. After about 12 months of use, the insulating formulationremained useable without conditioning and with no apparent degradation.

TABLE 1 Comparison of Energy Storage Density Time = 1 μsec Time = 10μsec Dielectic kV/ Energy Energy Fluid Constant cm Density kV/cm DensityInsulating 15 380 9.59E−02 325 7.01E−02 formulation Trans. Oil 2.2 5002.43E−02 235 5.38E−03 Water 80 600 1.27E+00 280 2.78E−01 Energy density= ½ * ∈ * ∈₀ * E_(bd) * E_(bd) ~ j/cm³6. Summary.

A summary of the dielectric properties of the insulating formulation ofthe present invention is shown in Table 2. Applications of theinsulating formulation include high energy density capacitors,large-scale pulsed power machines, and compact repetitive pulsed powermachines.

TABLE 2 Summary of Formulation Properties Dielectric Strength = 380kV/cm (1 μsec) Dielectric Constant = 15 Conductivity = 1e−6 mho/cm Waterabsorption = up to 2000 ppm with no apparent ill effects

The preceding examples can be repeated with similar success bysubstituting the generically or specifically described compositions,biomaterials, devices and/or operating conditions of this invention forthose used in the preceding examples.

Although the invention has been described in detail with particularreference to these preferred embodiments, other embodiments can achievethe same results. Variations and modifications of the present inventionwill be obvious to those skilled in the art and it is intended to coverall such modifications and equivalents. The entire disclosures of allreferences, applications, patents, and publications cited above, and ofthe corresponding application(s), are hereby incorporated by reference.

1. An assembly for creating a pressure pulse in a liquid-filled cavity within a boulder, said assembly comprising: a transducer assembly comprising a transducer case having a plurality of openings and at least one electrode set, said electrode set having at least one high voltage electrode and at least one low voltage electrode and defining at least one electrode gap therebetween; through which an electrical current passes to create pressure through expansion of the liquid as the liquid undergoes a phase change to gas and/or plasma; an energy storage component disposed directly in said transducer assembly, wherein said energy storage component is disposed directly adjacent to the boulder; and a primary electrical power source connected to said energy storage component for charging said energy storage component.
 2. The assembly of claim 1 further comprising a switch disposed in said transducer assembly to connect said energy storage component to said electrodes.
 3. The assembly of claim 1 wherein said primary electrical power source comprises a high voltage capacitor bank to provide a high voltage pulse via said cable to charge said energy storage component.
 4. The assembly of claim 3 wherein said capacitor bank comprises at least one switching component selected from the group consisting of a spark gap, a thyratron, a vacuum gap, a pseudo-spark switch, a mechanical switch, a solid state switch, and a combination thereof.
 5. The assembly of claim 1 wherein said energy storage component comprises an inductive energy storage component.
 6. The assembly of claim 1 comprising more than one set of electrodes arranged in parallel allowing parallel current flow.
 7. The assembly of claim 1 comprising more than one set of electrodes arranged in series.
 8. The assembly of claim 1 comprising more than one set of electrodes arranged in a geometric configuration.
 9. The assembly of claim 8 wherein said geometric configuration comprises a configuration selected from the group consisting of a straight line, a curve, a circle, a spiral, and a combination thereof.
 10. The assembly of claim 1 wherein said at least one electrode set is disposed in said transducer assembly with at least one intermediate electrode disposed between said high voltage electrode and said low voltage electrode so that capacitance is provided between at least one said intermediate electrode and a ground structure of said transducer assembly.
 11. The assembly of claim 10 wherein said capacitance is formed via a liquid disposed between said intermediate electrode and said ground structure.
 12. The assembly of claim 10 wherein said capacitance is formed via a capacitor disposed between said intermediate electrode and said ground structure.
 13. The assembly of claim 10 further comprising a liquid or capacitor between said at least one electrode to another electrode in said electrode set to form said capacitance.
 14. The assembly of claim 1 further comprising a cable connecting a primary electrical power source to said energy storage component.
 15. The assembly of claim 14 wherein said primary electrical power source comprises an inductive energy storage apparatus to provide a high voltage pulse via said cable to charge said energy storage component.
 16. The assembly of claim 14 wherein said primary electrical power source comprises an electrical power supply to provide a high voltage via said cable to charge said energy storage component.
 17. The assembly of claim 1 wherein said at least one electrode set is disposed in said transducer assembly so that capacitance is provided between said high voltage electrode and a ground structure of said transducer assembly.
 18. The assembly of claim 17 wherein said capacitance is formed via a liquid disposed between said intermediate electrode and said ground structure.
 19. The assembly of claim 17 wherein said capacitance is formed via a capacitor disposed between said intermediate electrode and said ground structure.
 20. The assembly of claim 17 further comprising a liquid or capacitor between said at least one electrode to another electrode in said electrode set to form said capacitance.
 21. The assembly of claim 1 wherein said energy storage component is disposed directly into a hole in said boulder.
 22. A method for creating a pressure pulse in a liquid-filled cavity within a boulder, the method comprising: providing a transducer assembly comprising a transducer case having a plurality of openings and at least one electrode set, the electrode set having at least one high voltage electrode and at least one low voltage electrode, and defining at least one electrode gap therebetween; disposing an energy storage component directly in the transducer assembly, increasing the peak current through the transducer; disposing the energy storage component directly adjacent to the boulder; delivering reduced electric current via a cable connected to the energy storage component; converting the electrical current into a plasma pressure source with improved efficiency via the at least one electrode set; and releasing and expanding the plasma pressure via the openings to break the boulder.
 23. The method of claim 22 further comprising connecting the energy storage component to the electrodes via a switch in the transducer assembly.
 24. The method of claim 22 further comprising providing a high voltage pulse via the cable by providing a high voltage capacitor bank.
 25. The method of claim 24 wherein the capacitor bank comprises a component selected from the group consisting of a spark gap, a thyratron, a vacuum gap, a pseudo-spark switch, a mechanical switch, and a combination thereof.
 26. The method of claim 22 further comprising providing a high voltage pulse via the cable by providing an inductive storage component.
 27. The method of claim 22 further comprising connecting the energy storage component to the electrodes by disposing a switch in the transducer assembly.
 28. The method of claim 22 comprising disposing the energy storage component in a hole in the boulder.
 29. A method for creating pressure waves in a liquid to a boulder, the method comprising: providing a transducer assembly, the transducer assembly comprising a transducer case having a plurality of openings and at least one electrode set, the electrode set having at least one high voltage electrode and at least one low voltage, wherein said at least one high voltage electrode or said at least one low voltage electrode comprises an intermediate electrode, and defining at least one electrode gap therebetween; disposing the transducer assembly adjacent to the boulder; passing an electrical current between the gap; thus creating pressure energy through expansion of liquid as the liquid undergoes a phase change to gas or plasma; improving the efficiency of converting electrical energy to pressure energy; and releasing and expanding the pressure energy via the openings to break the boulder.
 30. The method of claim 29 further comprising arranging more than one set of electrodes in parallel.
 31. The method of claim 29 further comprising arranging more than one set of electrodes in a line or series of straight lines.
 32. The method of claim 29 further comprising arranging more than one set of electrodes in a geometric configuration.
 33. The method of claim 32 further comprising selecting the geometric configuration from the group consisting of a straight line, a curve, a circle, a spiral, and a combination thereof.
 34. The method of claim 29 further comprising providing capacitance between each intermediate electrode and a ground structure of the transducer assembly by disposing the at least one electrode set in the transducer assembly.
 35. The method of claim 34 further comprising forming the capacitance by disposing a liquid between the intermediate electrode and the ground structure.
 36. The method of claim 34 further comprising forming the capacitance by disposing a capacitor between the intermediate electrode and the ground structure.
 37. The method of claim 36 wherein the capacitor comprises a solid or liquid dielectric material.
 38. The method of claim 34 further comprising forming the capacitance by disposing a liquid or capacitor between the at least one electrode set from electrode to electrode.
 39. The method of claim 34 further comprising supplying electrical energy to a multi-gap transducer by providing an integral energy storage module.
 40. The method of claim 39 further comprising connecting a cable to an energy storage device located away from the boulder.
 41. The method of claim 29 comprising disposing the energy storage component in a hole in the boulder. 